<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
	</head>
	<body>
		<input id="btn" type="button" value="我是一个按钮" onmouseover="over()" onmouseout="out()" />
	</body>
</html>
<script>
	var btn=document.getElementById("btn");
	//鼠标移入事件
	function over(){
		console.info("鼠标移入了");
		btn.style.width="200px";
		btn.style.height="60px";
	}
	//鼠标移出事件
	function out(){
		console.info("移出");
		btn.style.width="100px";
		btn.style.height="30px";
	}
</script>